A heretofore known Christmas lamp bulb fixing socket, as shown in FIG. 4, includes a connecting head 5 and a socket 6. connecting head 5 has a protrusion 51 on a top edge of an outward circumference thereof. The protrusion 51 is made of a flexible material such as a thin plastic, and has a hole 511 formed therethrough. The socket 6 has a protrusion 61 on a top edge of an outward circumference thereof, such that the protrusion 61 is fitted into the hole 511 to firmly connect both the connecting head 5 and the socket 6 after the head 5 is passed into the socket 6.
However, because the protrusion 51 is very thin and is frequently moved up and down through use, it loses its flexibility, and eventually can't be firmly fitted onto the protrusion 61. Moreover, the protrusions 51, 61 need to be specifically shaped with respect to the interval therebetween and curvature such that both can firmly connect, otherwise both can't mate very well. So, in terms of simplicity and efficiency, this kind of connection has disadvantages.